A cellular network is a collection of cells that each includes at least one base station capable of transmitting and relaying signals to subscriber's mobile devices. A “cell” generally denotes a distinct area of a cellular network that utilizes a particular frequency or range of frequencies for transmission of data. A typical base station is a tower to which are affixed a number of antennas that transmit and receive the data over the particular frequency. Mobile devices, such as cellular or mobile phones, smart phones, camera phones, personal digital assistants (PDAs) and laptop computers, may initiate or otherwise transmit a signal at the designated frequency to the base station in order to initiate a call or data session and begin transmitting data.
A backhaul network connects the base station to a gateway device. The backhaul network is the layer two (L2) network (from a mobile subscriber's perspective) that provides connectivity from the base station to the gateway device. Several cellular service providers are moving towards Internet Protocol (IP)/Multiprotocol Label Switching (MPLS) based mobile backhaul networks for Second Generation (2G), Third Generation (3G), and other wireless technologies. Microwave Access (WiMax) and Long Term Evolution (LTE) technologies are likely to move in this direction as well. For example, recently, cellular service providers have begun to upgrade cellular networks to support services, such as high-speed access to packet-based networks (e.g., the Internet), voice over Internet protocol (VoIP) and Internet protocol television (IPTV). To upgrade the cellular networks, cellular service providers convert cellular signals, e.g., Time Division Multiple Access (TDMA) signals, Orthogonal Frequency-Division Multiplexing (OFDM) signals or Code Division Multiple Access (CDMA) signals, received at a base station from mobile devices into Internet protocol (IP) packets for transmission within the packet-based networks. A number of standards have been proposed to facilitate this conversion and transmission of cellular signals to IP packets, such as a General Packet Radio Service (GPRS) standardized by the Global System for Mobile Communications (GSM) Association, Mobile IP standardized by the Internet Engineering Task Force (IETF), as well as other standards proposed by the 3rd Generation Partnership Project (3GPP), 3rd Generation Partnership Project 2 (3GGP/2) and the Worldwide Interoperability for WiMax forum.
“Micro mobility” is defined as mobility that is anchored at a fixed IP gateway device. The mobile device is in the micro mobility domain as long as its IP gateway does not change as the mobile device moves location, even though mobile device may communicate with different base stations and/or the Backhaul Network Gateways (BNG) used to reach the IP gateway. WiMax's micro mobility solution requires a new control protocol that involves the base station and the access services network (ASN) gateway (“R2 and R4 interface,” in WiMax terminology). “Macro mobility” is defined as mobility that allows a mobile node to move from one IP gateway to another while retaining its IP address. Existing macro mobility solutions use Mobile IP and extensions to Mobile IP, which have several limitations. Some existing macro mobility solutions include Client Mobile IP, Client Mobile IPv4, Proxy Mobile IPv4, Mobile IPv6, and Client Mobile IPv6.
Regardless of which standard a cellular service providers choose to adopt, each of the standards generally define a cellular network architecture in which a particular mobile device is associated with a specific gateway device and an anchor device. That is, upon initiating a packet-based data communication session, the mobile device is bound to both a gateway device and an anchor device within the cellular network architecture. Commonly, each gateway device is an IP gateway or other IP-enabled access router that is associated with one or more base stations proximate to the origin of the communication session. Through the transmission and relay capabilities of the base stations, each gateway device handles data session initiated by the mobile device and routes the IP communications to the packet-based networks. That is, the gateway device routes any data communication originated by the mobile device to the anchor device. This routing configuration involving a mobile device, gateway device, and an anchor device is referred to as “triangular routing.”
The anchor device is typically a service-oriented IP-enabled router that stores policies and other information (collectively, a “subscriber context”) that are specific to a particular mobile device. The subscriber context may define, for example, a level or quality of service, encryption keys, address information, multicast group memberships, and charging and accounting information to account for the services provided to the particular mobile device. The anchor device provides an “anchor” or a set location for subscriber-specific context information (referred to as “subscriber contexts”) required to access the packet-based network continuously while the associated mobile devices move through the cellular network. The anchor device may mark, tag, or otherwise processes the data communication in accordance with the subscriber context and then route the data communication to the intended destination within the packet-based network. In some cellular architectures, the gateway device may be referred to as a “foreign agent” while the “anchor device” may be referred to as a “home agent.”
While the above network architecture enables accurate charging and accounting, the continuous triangular routing of all data packets to the anchor device for a session may inject substantial delay into the delivery of the above described services and erode the quality of service provided to the mobile device. Thus, by associating the subscriber with a fixed anchor device, the above architectures inefficiently route traffic and likely cause delay in accessing the packet-based network and the services supported by the packet-based network. This deficiency may become particularly limiting as cellular base stations are upgraded to support higher transmission speeds because the added delay may form a bottleneck to achieving higher data transmission speeds and violate Quality of Service (QoS) agreements with the subscriber.